New Yorkers are used to seeing their skyscrapers all lit up around Christmastime, but the Flatiron yesterday was illuminated to celebrate not Santa, but—Pythagoras?

It's true. The Museum of Mathematics took to the street to prove that the Flatiron is, in fact, a right triangle that adheres to the Pythagorean theorem. Volunteers surrounded the perimeter of the building holding glow sticks that served as units of measurement. The building turned out to be 75 glow sticks long on the 23rd Street side, 180 glow sticks long on the 5th Avenue side, and 195 glow sticks long on the Broadway side. If you remember your a2 + b2 = c2, that means the Flatiron is a 5-12-13 right triangle (fitting, since the event happened on December 5, 2013, or 12/5/13, just a few days before the museum's first anniversary).

"We wanted to show that math is all around us, even in places we wouldn't expect," says Cindy Lawrence, MoMath's co-executive director. It was also a chance for math fans—yes, they're out there—to show off their stripes. Approximately 2,000 people attended, sporting right-triangle-themed T-shirts, hats, face paint, and even tattoos. "There's a social barrier out there that tells people it's not okay to like math," says co-executive director Glen Whitney. "We want to get over that barrier."

If you're sad that you didn't get to wear your favorite theorem T-shirt and socialize with other math boosters, rest assured that the "Pythagorize the Flatiron" event is just the first of the Museum's "Math Happenings," which it plans to continue into next year; visit momath.org to sign up to hear about future public displays of mathematics.